textproduct: Albany

WHAT HAS CHANGED

Tornado Watch #507 issued for western Adirondacks, mid-Hudson Valley, northern/eastern Catskills, Mohawk Valley and NW CT through 9PM tonight.

KEY MESSAGES

1) Widespread showers and thunderstorms are expected late this afternoon into the evening, with some scattered showers and storms returning tomorrow, especially west of the Hudson River. Storms will be capable of producing heavy downpours resulting in localized flooding as well as brief gusty winds, especially south and west of the Capital District.

2) Tranquil weather with temperatures trending slightly above normal Thursday into this weekend.

DISCUSSION

KEY MESSAGE 1...Widespread cloud coverage over eastern NY and western New England continues into this afternoon as we remain north of a sfc warm front positioned in far southeastern NY/northern NJ. However, the mid-level warm front has started to advance northeastward and dew points are creeping further into the upper 60s to low 70s. With the latest visible satellite showing some thinning to the cloud coverage, the increased insolation combined with an increasingly moist environment is contributing to increased instability. The latest SPC mesoscale analysis shows meager ML CAPE values around 500 - 1000 J/kg mainly south and west of the Hudson River with instability quickly trending downwards into the Capital District and north and east. PWATs are quite high today well over 1.5" as the latest ALPW satellite channels show a moisture plume from the Southeast U.S and western Atlantic nosing northward. Forecast soundings also show that this highly moist environment will also feature high freezing level heights 12-13 kft and high EL heights supporting a tall- skinny CAPE sounding. With effective shear also decent at 25 - 35kts, today is a classic environment that favors heavy downpours and this continues to be the primary hazard for today. We considered a flood watch for the mid- Hudson Valley where WPC maintains its slight risk in the Day 1 Excessive Rainfall Outlook; however, decided to hold off given this area missed out on the heavy rain this morning and it remained mainly to the south. While the latest 3-hrly precipitation PMM from the HREF still shows a 10 to localized 30% chance for 3" of rain in three hours in the mid-Hudson Valley and eastern Catskills late this afternoon into this evening, the latest 3-hr FFG remain quite high at 2.5 - 3.5". Thus, even if these rainfall rates are realized, rainfall amounts may just reach FFG. If heavy rain repeatedly impacts a given area, it will likely become vulnerable to localized flooding including even isolated to scattered flash flooding but confidence is too low to warrant a flood watch.

Besides heavy rain resulting in localized flooding, severe thunderstorms resulting in damaging winds is a secondary hazard for today. As was mentioned, forecast sounding overall meager instability with the highest values south/east of the Capital District. However, favorable effective shear 30 - 40kts combined with sufficient instability can support bowing segments and QLCS type structures as the warm front lifts northward. Damaging winds are the primary hazard from any severe storms but southeast winds in the low-levels quickly veering to the west-southwest aloft have led to curved hodographs and enhanced effective helicity values along the warm front to 100-200m2/s2. This means isolated tornadoes are not ruled out, especially given low LCLs values. Thus, we have collaborated with SPC and neighboring WFOs to issue a Tornado Watch through 9PM this evening for the Mohawk Valley, western Adirondacks, northern and eastern Catskills, mid-Hudson Valley and NW CT. Very high EL heights also makes this a favorable environment for frequent lightning. Latest CAMs have struggled capturing latest radar trends but as convection from the Southern Tier and southeast NY tracks north and east later this afternoon, it will run into a less favorable environment and weaken. Thus, the latest Tornado Watch does not extend into the Capital District or areas north and east. Any initial strong to severe storms should weaken late this afternoon as the environments gets worked over and transition to more of a hydro concern. Some showers will still be around tonight as the warm front finally pushes north and east but will diminish in coverage. Otherwise, it will remain very muggy.

The warm sector shifts eastward tomorrow as the main cold front and trough axis swings into the Northeast. Given the early arrival of the cold front pushing into the eastern NY by 15 - 18 UTC, the highest chance for the warm sector to have enough time to destabilize before the strongest forcing arrives look to be in areas mainly east of the Hudson River, especially in western New England. The latest Day 2 SPC Outlook continues to place a marginal (level 1 of 5) risk for severe weather in southern Berkshire and Litchfield Counties where there is a favorable overlap of 500-1000J/kg of SB CAPE and 40-45kts of deep layer shear. Latest CAMs shows an initial line of showers developing along the incoming cold front late morning that grows upscale into line segments and storm clusters as it enters western New England and the more unstable environment mainly after 17-18 UTC. Damaging winds will also again be the main hazard through late afternoon before the front finally pushes eastward into New England. Otherwise, humidity will trend downwards behind the cold front from west to east through the day with clearing skies.

KEY MESSAGE 2...We will enjoy a stretch of pleasant and dry weather Thursday through this weekend as high pressure builds overhead. Temperatures trend upwards Friday into the weekend as high pressure builds off shore promoting southwesterly return flow but we do not expect oppressive heat. Another shortwave approaches late this weekend into early next week but there is still uncertainty on timing and placement of any showers or convection.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Through 18Z Wednesday... MVFR conditions prevail across all terminals throughout this afternoon and evening, driven by lower cigs from rain showers. Moderate winds out of the south to southwest with gusts up to 20-25 kts will also prevail across all terminals through the first several hours of this TAF period. There is a chance of thunderstorms this evening at all terminals, which could bring periods of IFR vis, lower cigs, and stronger winds/gusts. As rain and storms begin to taper out in the overnight hours, low-level moisture is expected to stick around, leading to widespread/marginal IFR cigs at all terminals, although vis will begin to improve throughout this period. Winds will also slightly weaken overnight and will start to veer to out of the southwest.

Conditions are expected to gradually improve after sunrise on Wednesday, with cigs rising back up to MVFR and VFR at all terminals by the early afternoon hours. Winds are expected to strengthen again on Wednesday morning and early afternoon, with the return of gusts up to 15-25 kts, while shifting to prevail out of the west.

Outlook...

Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.